Image projection apparatus capable of preventing image which would  be hindrance to viewing printed material from being projected on  printed material, control method therefor, and storage medium

ABSTRACT

An image projection apparatus which is capable of preventing an image which would be a hindrance to viewing printed material from being projected on the printed material. Based on input image data, a projection unit projects a projected image. Whether or not the printed material is placed on a screen at a projection destination of light projected by the projection unit is determined. The projection unit is controlled based on a result of the determination.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 15/926,908,filed Mar. 20, 2018, the entire disclosure of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an image projection apparatus, acontrol method therefor, and a storage medium.

Description of the Related Art

High dynamic range images (hereafter referred to as “HDR images”) withhigh dynamic range has high expressive power in terms of color,gradations, textures, and so forth, and hence they are used in variousscenes in increasing opportunities. Accordingly, various techniques toregenerate images taken by digital cameras and the like as HDR imageshave been proposed. For example, with the aim of extending the dynamicrange of luminance and color gamut, there has been proposed a techniquethat forms an image to be observed (hereafter referred to as a“superimposed image”) with contrast improved by projecting apredetermined image onto printed material by means of an imageprojection apparatus (projector) (see, for example, Japanese Laid-OpenPatent Publication. (Kokai) No. 2008-83180). On the other hand, therehas also been proposed a technique that projects blue or white light ina case where no image data on an image for use in projection has beeninput to the image projection apparatus (see, for example, JapaneseLaid-Open Patent Publication (Kokai) No. 2006-3426).

The technique described in Japanese Laid-Open Patent Publication (Kokai)No. 2008-83180, however, has a problem that in a case where the imageprojection apparatus has no image data on an image for use in projectionwhen an image is to be projected onto the printed material, an imageunrelated to the printed material is projected, and therefore, desiredcontrast cannot be achieved. The technique described in JapaneseLaid-Open Patent Publication (Kokai) No. 2006-3426 also has a problemthat when it is detected that image data for use in projection has notbeen input to the image projection apparatus, blue light that indicatesoccurrence of an abnormal condition is projected, and this would be ahindrance to viewing the printed material.

SUMMARY OF THE INVENTION

The present invention provides an image projection apparatus which iscapable of preventing an image which would be a hindrance to viewingprinted material from being projected on the printed material, a controlmethod therefor, and a storage medium.

Accordingly, the present invention provides an image projectionapparatus comprising a projection unit configured to project a projectedimage based on input image data on a screen, a first determining unitconfigured to determine whether or not printed material is placed on thescreen at a projection destination of light projected by the projectionunit, and a control unit configured to control the projection unit basedon a result of a determination by the first determining unit.

According to the present invention, an image which would be a hindranceto viewing printed material is prevented from being projected on theprinted material.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically showing an arrangement of animage projection apparatus according to a first embodiment of thepresent invention.

FIG. 2 is a flowchart useful in explaining how projection is controlledby the image projection apparatus in FIG. 1.

FIGS. 3A to 3D are views showing examples of images projected by theimage projection apparatus in FIG. 1 and destinations onto which imagesare projected by the image projection apparatus in FIG. 1.

FIG. 4 is a block diagram schematically showing an image projectionapparatus according to a second embodiment of the present invention.

FIG. 5 is a flowchart useful in explaining how projection is controlledby the image projection apparatus in FIG. 4.

FIGS. 6A and 6B are views showing examples of images projected by theimage projection apparatus in FIG. 4.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings.

FIG. 1 is a block diagram schematically showing an arrangement of animage projection apparatus 100 according to a first embodiment of thepresent invention. The image projection apparatus 100 has an input unit102, an image input detecting unit 103, a sensor 104, a printed materialdetecting unit 105, a determining unit 106, a light source unit 107, anda light source control unit 108. The image projection apparatus 100 alsohas a liquid crystal device unit. 109, a liquid crystal control unit110, a projection unit 111, a memory 112, a CPU 113, and a data bus 120.

The input unit 102 receives image data (image signals) sent fromexternal devices such as a personal computer (PC), a smart phone, and adigital camera, not shown. The image data may be either image data on astill image or image data on frames (images) constituting a video signal(moving images). The image data obtained by the input unit 102 istemporarily stored in the memory 112. The input unit 102 is capable ofobtaining image data from a database (such as a server) on a network,not shown, to which the image projection apparatus 100 is connected.Further, the input unit 102 is capable of obtaining image data stored ina memory card, a hard disk, and the like, not shown.

The image input detecting unit 103 detects the presence or absence of animage input to the input unit 102 and notifies the determining unit 106and the CPU 113 of the detection result. The sensor 104 is an imagesensor (camera) which shoots a destination of projection by theprojection unit 111, and captures an image. Image data generated fromthe image captured by the sensor 104 is stored in the memory 112.

By subjecting an image captured by the sensor 104 to image processing,the printed material detecting unit 105 determines whether or notprinted material, which is a target for projection, is placed at adestination of projection by the projection unit 111. For example, auser shoots in advance a placement destination such as a wall surface onwhich the printed material is to be placed (posted) and registers animage captured by shooting (hereafter referred to as “the image B”) inthe memory 112. The printed material detecting unit 105 then calculatesa value of correlation between the image B and an image obtained by thesensor 104 shooting a destination of light projected from the projectionunit 111 (hereafter referred to as “the image A”). For example, tocalculate the value of correlation, the printed material detecting unit105 calculates absolute values of differences (hereafter referred to as“SAD”) between pixels of the image A and the image B. A value of SADbetween the image A and the image B is calculated according to anequation 1 below, where X [pixels] represents the width of the image,and Y [pixels] represents the height of the image.

[Mathematical Expression 1]

SAD=Σ₁ ₁ ₁ ¹Σ₁ ₁ ₁ ¹ ∥A(x,y)−B(x,y)∥  Equation 1

In the above equation 1, A(x, y) and B(x, y) represent luminance valuesof pixels at coordinates (x, y) of the images A and B, respectively. Thesmaller the value of SAD between the images A and B calculated accordingto the above equation 1, the higher the correlation between the images Aand B (between the two images compared with each other). Conversely, thegreater the value of SAD between the images A. and B calculatedaccording to the above equation 1, the lower the correlation between theimages A and B. Accordingly, when the value of SAD is equal to orgreater than a threshold value determined in advance, the CPU 113determines that the printed material is placed at the destination ofprojection from the projection unit 111, and when the value of SAD issmaller than the threshold value, the CPU 113 determines that theprinted material is not placed at the destination of projection from theprojection unit 111. The printed material detecting unit 105 thusascertains whether the printed material is present or absent at thedestination of projection from the projection unit 111. It should benoted that a correlation between an image formed on the printed materialand the image B may be determined by obtaining the value of SAD.

It should be noted that in a case where a variety of images are storedin the memory 112 daring manufacturing of the image projection apparatus100 (at the time of shipment), a wall surface or the like on which theprinted material is to be placed does not always have to be shot inadvance. For example, the user may designate an image regarded as adestination of projection from the projection unit 111, depending on acondition (mode) of a projection destination of light from theprojection unit 111. In this case, however, in order to determine acorrelation between an image registered at the time of shipment and amimage of the projection destination shot by the sensor 104, their imagesizes need to be made equal.

The determining unit 106 determines whether or not projection of animage designated in advance as an image to be projected onto the printedmaterial (hereafter referred to a “projected image”) is possible. Forexample, when the image input detecting unit 103 detects that input ofimage data to the input unit 102 stops during projection based on imagedata on the projected image, the determining unit 106 determines thatthe projection has become impossible. Specifically, when networkcommunication stops when an image obtained from a network connected tothe input unit 102 is being displayed and communication has becomeimpossible, the determining unit 106 determines that the projection hasbecome impossible. Also, when input of image data stops due to, forexample, removal of a storage medium connected to the input unit 102when an image obtained from the storage medium is being displayed, thedetermining unit 106 determines that the projection has becomeimpossible. When the printed material is not placed at a predeterminedposition or when the printed material on which an image different fromthe projected image is formed is placed, the determining unit 106 alsodetermines that the projection has become impossible. Further, whenimage data on the projected image is absent in the memory 112, thedetermining unit 106 determines that the projection is impossible. Thedetermining unit 106 notifies thP CPU 113 of the judgment result.

The light source unit 107 is a laser, an LED, a halogen lamp, a xenonlamp, a high-pressure mercury lamp, or the like and outputs light foruse in projection by the projection unit 111. The light source controlunit 108 controls turning on-off and brightness of the light source unit107. The liquid crystal device unit 109 has one liquid crystal panel foreach of red (R), green (G), and blue (B) color components. Based onimage data input from the memory 112, the liquid crystal control unit110 controls voltage applied to pixels (R pixels, G pixels, and Bpixels) of the liquid crystal device unit 109 to adjust reflectance andtransmittance on a pixel-by-pixel basis. The projection unit 111, whichis comprised of, for example, a dichroic mirror or a prism, combines R,G, and B beams that have passed through the respective RGB liquidcrystal panels constituting the liquid crystal device unit 109. Theprojection unit 111 externally radiates the combined beams through aprojection optical system, not shown, comprised of a lens or the like,and as a result, an image read from the memory 112 is projected onto apredetermined position on a screen (a wall). At this time, the liquidcrystal device unit 109 is controlled by the liquid crystal control unit110 so as to have light transmittance corresponding to the image readfrom the memory 112.

The CPU 113 integrally controls operation of the image projectionapparatus 100 by executing predetermined programs stored in the memory112 to control operation of the components of the image projectionapparatus 100. The memory 112 stores image data, programs which areexecuted by the CPU 113, and so forth. The data bus 120 connects thecomponents constituting the image projection apparatus 100 with oneanother so that they can communicate with one another. It should benoted that the image input detecting unit 103, the printed materialdetecting unit 105, the determining unit 106, the light source controlunit 108, and the liquid crystal control unit 110 may be eachimplemented either by software (programs) or by hardware. Each of thesecomponents may also be implemented by a combination of software andhardware or may be comprised of a microcomputer or an arithmetic devicesuch as an ASIC.

The image projection apparatus 100 is controlled by the CPU 113 so as toswitch modes of projection from the projection unit 111 according towhether or not printed material is present on the screen at a projectiondestination and whether or not projection of an image from theprojection unit 111 is possible. FIG. 2 is a flowchart useful inexplaining how projection is controlled by the image projectionapparatus 100. Here, it is assumed that a position at which printedmaterial is placed and a position at which an image from the imageprojection apparatus 100 is projected are aligned in advance. Processesin the flowchart of FIG. 2 are implemented by the CPU 113 of the imageprojection apparatus 100 executing predetermined programs stored in thememory 112 to control operation of the components constituting the imageprojection apparatus 100.

In step S201, based on a result of judgment by the determining unit 106,the CPU 113 determines whether or not projection of a projected image ispossible. It should be noted that the criterion for judgment by thedetermining unit 106 as to whether the projection is possible orimpossible has already been described, and therefore, description isomitted here. When the CPU 113 determines that the projection of theprojected image possible (YES in step S201), the process proceeds tostep S205, and when the CPU 113 determines that projection of theprojected image is impossible (NO in the step S201), the processproceeds to step S202.

In the step S202, based on a result of detection by the printed materialdetecting unit 105, the CPU 113 determines whether or not printedmaterial is placed on the screen at a projection destination. When theCPU 113 determines that the printed material detecting unit 105 hasdetected printed material (YES in the step S202), the process proceedsto step S203, and when the CPU 113 determines that the printed materialdetecting unit 105 has detected no printed material (NO in the stepS202), the process proceeds to step S204.

In the step 3203, the CPU 113 projects white light from the projectionunit 111 onto the printed material, thus widening a dynamic range of theprinted material. It should be noted that the white light means light inwhich visible light of blue (shorter wavelengths) to red (longerwavelengths) wavelengths is substantially uniformly mixed. In the stepS204, the CPU 113 determines that an abnormal condition that makes theprojection impossible occurs, and then projects blue light from theprojection unit 111 onto the whole surface of the projectiondestination. As a result, the user knows that an abnormal conditionoccurs in the image projection apparatus 100. In the step S205, the CPU113 projects the projected image stored in the memory 112 onto theprinted material, and this forms a superimposed image (image to beobserved) that is the printed material with its dynamic range widened.

After the steps S203, S204, and S205, the CPU 113 determines in stepS206 whether or not to end the projection. For example, when the userhas instructed the CPU 113 to end the projection by operating anoperating means, not shown, provided in the image projection apparatus100, the CPU 113 ends the projection. Upon judging that it has beeninstructed to end the projection (YES in the step S206), the CPU 113ends the present process, and when the CPU 113 determines that it hasnot been instructed to end the projection (NO in the step S206), theprocess returns to the step S201.

A description will now be given of concrete examples of the processcarried cut in accordance with the flowchart of FIG. 2. FIGS. 3A to 3Dare views showing examples of a projected image and a projectiondestination, FIGS. 3A and 3B showing the first example, and FIGS. 3C and3D showing the second example.

In the first example, it is assumed that no image data has been input tothe input unit 102. In this case, the judgment result in the step S201is negative (NO). FIG. 3A shows printed material 301 placed on thescreen at a projection destination. Since the printed material 301 isplaced at the projection destination, the judgment result in the stepS202 is positive (YES), and as a result, white light is projected ontothe printed material 301 in the step S203. FIG. 3B schematically shows awhite projected image 302 that is to be projected onto the printedmaterial 301. The CPU 113 controls the liquid crystal device unit 109via the liquid crystal control unit 110 such that the white projectedimage 302 is projected onto the printed material 301.

In the second example, it is assumed that no image data has been inputto the input unit 102 as with the first example. In this case, thejudgment result in the step S201 is negative (NO). FIG. 3C schematicallyshows a state in which no printed material is placed on the screen at aprojection destination. Here, a situation in which a wall surface 321 (awall surface or the like on which the printed material 301 is to beplaced) is the projection destination is taken up as an example. Sinceno printed material being placed at the projection destination, thejudgment result in the step S202 is negative (NO), and as a result, bluelight is projected onto the wall surface 321 in the step S204. FIG. 3Dschematically shows a blue projected image 302 that is to be projectedonto the wall surface 321. The CPU 113 controls the liquid crystaldevice unit 109 via the liquid crystal control unit 110 such that theblue projected image 322 is projected onto the wall surface 321.

As described above, in the present embodiment, as long as predeterminedprinted material is placed at the projection destination, white light isprojected onto the printed material without canceling projection orwithout projecting blue light even if no image data on an image to beprojected onto the printed material has been input, and this improvescontrast of the printed material. Thus, an image that would be ahindrance to viewing the printed material is prevented from beingprojected onto the printed material even though the printed material isplaced at the projection destination.

FIG. 4 is a block diagram schematically showing an arrangement of animage projection apparatus 400 according to a second embodiment of thepresent invention. Component elements of the image projection apparatus400 which are the same as those of the image projection apparatus 100are designated by the same reference symbols, detailed description ofwhich, therefore, is omitted. The image projection apparatus 400 has aninput unit 102, an image input detecting unit 103, a determining unit106, a light source unit 107, a light source control unit 108, a liquidcrystal device unit 109, a liquid crystal control unit 110, a projectionunit 111, a memory 112, a CPU 113, and a data bus 120. The imageprojection apparatus 400 also has a setting unit 401, a generating unit402, and a combining unit 403.

The setting unit 401 sets projection modes. Here, there are twoprojection modes consisting of a normal projection mode and a printedmaterial projection mode. In the normal projection mode, noconsideration is given to a projection destination. The printed materialprojection mode aims to project a projected image onto printed materialplaced on the screen at a projection destination. A detailed descriptionwill be given later of how the image projection apparatus 400 works inthe printed material projection mode.

The generating unit 402 generates graphics (images) for displaying anoperating menu for the image projection apparatus 400, selectivelydisplaying input signals, displaying a description of an image formed onprinted material on the screen at a projection destination, displaying awarning, and displaying other things. The CPU 113 stores the graphicsgenerated by the generating unit 402 in the memory 112. Based on aninstruction from the CPU 113, the combining unit 403 combines projectiondata with the graphics generated by the generating unit 402 and storedin the memory 112 to generate a composite image. The projection data maybe any of the following: image data on an image to be projected ontoprinted material, image data on a white fixed color image (image forprojecting white light onto the whole surface), and image data on a bluefixed color image (image for projecting white blue onto the wholesurface). The CPU 113 stores the composite image obtained by thecombining unit 403 in the memory 112.

In the first embodiment described earlier, the projection modes areswitched according to the presence or absence of image data on an imageto be projected onto printed material and the presence or absence ofprinted material on the screen at a projection destination. On the otherhand, in the present embodiment, the projection modes are switchedaccording to the presence or absence of image data on an image to beprojected onto printed material and a projection mode set for the imageprojection apparatus 400.

FIG. 5 is a flowchart describing how projection is controlled by theimage projection apparatus 400. Here, the image projection apparatus 400is configured to project no composite image when it is placed in theprinted material projection mode. Thus, the image projection apparatus400 is allowed to project only a composite image obtained by combininggraphics with the blue fixed color image as will be described later.Processes in the flowchart of FIG. 5 are implemented by the CPU 113executing predetermined programs stored in the memory 112 to controloperation of the components constituting the image projection apparatus400. It should be noted that processes in the flowchart FIG. 5 which arethe same as those in the flowchart of FIG. 2 will be briefly explainedby noting as such.

In step S501, based on a result of judgment by the determining unit 106,the CPU 113 determines whether or not projection of a projected imageonto printed material is possible. In the judgment in the step S501,whether the normal projection mode or the printed material projectionmode is set as the projection mode does not matter. Here, the imageprojection apparatus 400 does not ascertain whether or not printedmaterial is placed, and hence the determining unit 106 determines thatthe projection is possible as long as image data on the projected imageis stored in the memory 112. It should be noted that when an error thatmakes the projection of the projected image impossible occurs in theimage projection apparatus 400 even though the image data on theprojected image is stored in the memory 112, the determining unit 106determines that projection is impossible. Examples of the erroroccurring in the image projection apparatus 400 include an image dataformatting error.

When the determining unit 106 determines that the projection is possible(YES in the step S501), the CPU 113 proceeds to step S506. In the stepS506, the CPU 113 projects the projected image from the projection unit111 as with the process in the step S205, and after that, the processproceeds to step S507.

When the determining unit 106 determines that the projection isimpossible (NO in the step S501), the process proceeds to step S502. Inthe step S502, the CPU 113 determines whether or not the printedmaterial projection mode is set as the projection mode. The projectionmode is set by the user, and it is assumed that when the printedmaterial projection mode is not set, the normal projection mode is set.When the CPU 113 determines that the printed material projection mode isset (YES in the step S502), the process proceeds to step S503, and whenthe CPU 113 determines that the normal projection mode is set (NO in thestep S502), the process proceeds to step S504. It should be noted thatwhen the process proceeds to the step S504, the CPU 113 causes thegenerating unit 402 to generate graphics for notifying the user of thereason why the projection is impossible (for example, there is no imagedata on a projected image) and stores the generated graphics in thememory 112.

In the step S503, the CPU 113 reads out the white fixed color imagestored in the memory 112 at the time of shipment and projects whitelight from the projection unit 111 onto the whole surface by controllingthe liquid crystal control unit 110. It should be noted that in manycases, the printed material projection mode is set based on theprecondition that printed material is placed or has been placed at apredetermined position, and hence in the step S503, white light isprojected onto printed material in many instances. Projected white lightmixed with graphics tends to be a hindrance to viewing the printedmaterial, and hence in the present embodiment, the combining unit 403does not combine graphics with an image for projecting white light.After the step S503, the CPU 113 proceeds to step S507.

In the step S504, the CPU 113 reads out the blue fixed color image,which is stored in the memory 112 at the time of shipment, and projectsblue light from the projection unit 111 onto the whole surface bycontrolling the liquid crystal control unit 110. Then, in the next stepS505, first, the CPU 113 causes the combining unit 403 to combine thegraphics, which were stored in the memory 112 when the judgment resultin the step S502 was negative (NO), with the blue fixed color image togenerate a composite image. Then, in the step S505, the CPU 113 projectsthe generated composite image. As a result, the graphics are displayedas an OSD on the blue screen. Examples of the OSD displayed on the bluescreen include a notification indicating that there is no image data ona projected image, and a notification indicating that an error occurs inthe image projection apparatus 400. After the step S505, the CPU 113proceeds to the step S507.

The process in the step S507 is the same as the process in the stepS206, in which the CPU 113 determines whether or not to end theprojection. When the CPU 113 determines that it has been instructed toend the projection (YES in the step S507), the present process is ended,and when the CPU 113 determines that it has not been instructed to endthe projection (NO in the step S507), the process returns to the stepS501.

A description will be given of concrete examples of the process carriedout in accordance with the flowchart of FIG. 5. FIG. 6A is a viewschematically showing a white projected image 601 projected in the stepS503. In the step S503, the white projected image 601 is projected whenthe printed material projection mode is set although the projection isimpossible, and therefore, it does not matter whether or not printedmaterial is placed on the screen at a projection destination. Moreover,no OSD is displayed since the printed material projection mode is set.FIG. 6B is a view schematically showing a composite image projected inthe steps S504 and S505. In this example, graphics saying “no signaldetected” indicating the absence of image data on a projected image iscombined with a blue projected image 621, but the graphics to bedisplayed are not limited to them.

In the present embodiment, when white light is to be projected in theprinted material projection mode, a composite image obtained fromgraphics is not projected, but alternatively, a composite image in whichgraphics are placed at such a position as not to overlap an image formedon printed material may be projected. Examples of graphics to becombined with an image onto which white light is projected include anexplanation about the printed material. In this case, at the time ofprojection, graphics may be caused to show up outside the printedmaterial by adjusting a zoom rate of a lens, not shown, which theprojection unit 111 has. Likewise, although in the embodiment describedabove, graphics are combined with the inside of the blue projected image621 (FIG. 6B), a composite image may be generated such that graphics aredisplayed outside the blue projected image 621.

As described above, according to the present embodiment, even in a casewhere there is no image data on a projected image, white light isprojected as long as the printed material projection mode is set. As aresult, in a case where printed material is placed, a dynamic range ofthe printed material is widened. Even in a case where image projectiononto printed material becomes impossible although a projected image hasbeen normally projected onto the printed material, white light isprojected as long as the printed material projection mode is set,enabling the user to continue viewing the printed material. On the otherhand, when image projection onto printed material becomes impossiblealthough a projected image has been normally projected onto the printedmaterial, an OSD is displayed on a blue background as long as the normalprojection mode is set, and this immediately informs the user of theoccurrence of an abnormal condition.

It should be noted that although in the embodiments described above,blue light which is an example of chromatic light is projected by theprojection unit 111 in the steps S204 and S504, this is not limitative,but light in a chromatic color such as red, green, brown, dark red,violet, or navy blue may be projected. Moreover, the embodimentsdescribed above are merely illustrative embodiments of the presentinvention, and the embodiments may be used in combination asappropriate. For example, the image projection apparatus 100 may beequipped with the generating unit 402 and the combining unit 403 togenerate graphics for displaying a warning or the like, and when bluelight is projected, the graphics may also be projected as an OSD at thesame time.

Other Embodiments

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2017-057458, filed Mar. 23, 2017 which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A projection apparatus comprising: a projectionunit configured to project an image on a screen; and at least oneprocessor and/or at least one circuit that performs operations offollowing: determining whether or not image data is input; determining acondition of the screen; in a case that the image data is not input,controlling the projection unit based on the condition of the screen. 2.The projection apparatus according claim 1, wherein the at least oneprocessor and/or at least one circuit further performs operations offollowing: determining whether or not an object is on the screen, in acase that the image data is not input and the object is not on thescreen, controlling the projection unit to project a first image on thescreen, and in a case that the image data is not input and the object ison the screen, controlling the projection unit to project a second imageon the screen.
 3. The projection apparatus according claim 2, whereinthe object is printed material.
 4. The projection apparatus accordingclaim 2, wherein the first image is a color image, and the second imageis a white image.
 5. A projection apparatus comprising: a projectionunit configured to project an image on a screen; and at least oneprocessor and/or at least one circuit that performs operations offollowing: setting a projection mode; determining whether or not imagedata is input; in a case that the image data is not input, controllingthe projection unit based on the set projection mode.
 6. The projectionapparatus according claim 5, wherein the at least one processor and/orat least one circuit further performs operations of following: in a casethat the image data is not input and the set projection mode is a firstprojection mode, controlling the projection unit to project a firstimage on the screen, and in a case that the image data is not input andthe set projection mode is a second projection mode, controlling theprojection unit to project a second image on the screen.
 7. Theprojection apparatus according claim 6, wherein the first image is acolor image, and the second image is a white image.
 8. A control methodfor a projection apparatus having a projection unit configured toproject an image on a screen, the control method comprising: determiningwhether or not image data is input; determining a condition of thescreen; in a case that the image data is not input, controlling theprojection unit based on the condition of the screen.
 9. The controlmethod according claim 8, further comprising: determining whether or notan object is on the screen; in a case that the image data is not inputand the object is not on the screen, controlling the projection unit toproject a first image on the screen; and in a case that the image datais not input and the object is on the screen, controlling the projectionunit to project a second image on the screen.
 10. The control methodaccording claim 9, wherein the object is printed material.
 11. Thecontrol method according claim 9, wherein the first image is a colorimage, and the second image is a white image.
 12. A control method for aprojection apparatus having a projection unit configured to project animage on a screen, the control method comprising: setting a projectionmode; determining whether or not image data is input; and in a case thatthe image data is not input, controlling the projection unit based onthe set projection mode.
 13. The control method according claim 12,further comprising: in a case that the image data is not input and theset projection mode is a first projection mode, controlling theprojection unit to project a first image on the screen; and in a casethat the image data is not input and the set projection mode is a secondprojection mode, controlling the projection unit to project a secondimage on the screen.
 14. The control method according claim 13, whereinthe first image is a color image, and the second image is a white image.15. A con-transitory computer-readable storage medium storing a programfor causing a computer to execute a control method for a projectionapparatus having a projection unit configured to project an image on ascreen, the control method comprising: determining whether or not imagedata is input; determining a condition of the screen; in a case that theimage data is not input, controlling the projection unit based on thecondition of the screen.
 16. A non-transitory computer-readable storagemedium storing a program for causing a computer to execute a controlmethod for a projection apparatus having a projection unit configured toproject an image on a screen, the control method comprising: setting aprojection mode; determining whether or not image data is input; and ina case that the image data is not input, controlling the projection unitbased on the set projection mode.